1. Field of the Invention
The present invention relates to a manuscript scanner included in a copy machine, an image scanner, a facsimile, etc. and particularly to an automatic document feeder for automatically feeding a manuscript to be scanned.
2. Description of the Related Art
Conventional manuscript scanners for a copy machine, an image scanner, a facsimile machine, etc. have a transparent plate (for example, a glass plate) as a manuscript scanning surface on which a manuscript is placed and scanned, and a platen cover for covering the manuscript scanning section to shut off the ambient light when scanning. There are two ways for placing a manuscript on the transparent plate of the manuscript scanning section: one being for the user to manually and directly place the manuscript on the plate of the manuscript scanning section, the other being for an automatic document feeder to supply the manuscript to the manuscript scanning section. In the former case, it is required to open the platen cover when placing or taking out the manuscript and shut the platen cover when scanning, and in order to meet this requirement, the platen cover is mounted on the housing of the manuscript scanning section so as to allow opening and shutting operations through a hinge mechanism.
The automatic document feeder, in contrast, is commonly constructed to be fitted on the platen cover to avoid an increase in the size and complexity of the manuscript scanner and further to shorten the feed distance of the manuscript to facilitate the feed operation and also simplify the structure. In this case, there is a structure in which a manuscript stacker for stacking manuscripts to be fed is disposed on the platen cover and the manuscripts that have been scanned are discharged on the platen cover.
In the structure in which the automatic document feeder is fitted on the platen cover, the automatic document feeder and platen cover are opened and shut as one unit. As a result, the platen cover fitted with the automatic document feeder is heavy as compared to the structure in which solely a platen cover is opened and shut, entailing difficulty in handling the platen cover unless the user holds it firmly by hand during the opening and shutting operations.
For this reason, there is a structure in which concave portions 22 are formed in platen cover 21 as illustrated in FIG. 1 and FIG. 2 to assist the user to facilitate holding it by hand (cf. Japanese Patent Laid-open No. 2002-152462) and a structure in which a handle is provided (cf. Japanese Patent Laid-open No. 93076/83).
In the case where it is unnecessary to provide a manuscript discharging section on a platen cover, as with the structure described in Japanese Patent Laid-open No. 93076/83, it will suffice to construct the platen cover and manuscript stacker so that they have a sufficient strength. In recent years, however, there has been a main tendency to adopt the structure in which manuscript discharging section 23 is provided on a platen cover 21, as described above, to achieve reduction in size and weight of the platen cover (cf. FIG. 1.) In the structure in which the manuscript stacker 24 is located on the platen cover 21 and the scanned manuscripts are discharged into the space (manuscript discharging section 23) on the platen cover 21, it is necessary for the user to insert a hand into the space between platen cover 21 and manuscript stacker 24 (manuscript discharging section 23) when the manuscript which has been scanned and discharged into the space is taken out. In order to facilitate removal of the manuscript, platen cover 21 has been formed thin as described in Japanese Patent Laid-open No. 2002-152462.
In the above structure, it is difficult to balance competing goals of both providing concave section 22, in platen cover 21, that has large enough dimensions to allow a user to lift it up by inserting a hand into concave section 22 in order to open and shut platen cover 21, and keeping sufficiently large space (manuscript discharging section 23) for the user to remove a manuscript with a hand which is inserted between platen cover 21 and manuscript stacker 24. In other words, concave section 22 is formed to protrude upward toward manuscript stacker 24, which narrows the entrance of manuscript discharging section 23. The position of concave section 22 is set up to the front of platen cover 21 which makes it easy for the user to handle, while the position is also suitable for the user to insert a hand into manuscript discharging section 23. For this reason, if the user inserts a hand into manuscript discharging section 23 from a position away from concave section 22, such operation is troublesome to the user. After all, unless the space between platen cover 21 and manuscript stacker 24 is sufficiently enlarged entailing an increase in the size of the device, it is difficult to attain both goals for facilitating the removal of a discharged manuscript after scanning and facilitating the opening and shutting operations of automatic document feeder 25 and platen cover 21.
If concave section 22 of platen cover 21 is formed in a size and a shape that is hard to handle, or disposed in a position that is hard to handle, as a result of facilitating the removal of a manuscript, the user might possibly perform opening and shutting operation of automatic document feeder 25 and platen cover 21 by grasping any other portion of platen cover 21 other than concave section 22. The user in many cases holds the platen cover 21 particularly while grasping the front portion of manuscript stacker 24. Manuscript stacker 24 itself, however, is in many cases constructed so that it can swing relative to platen cover 21 by means of a hinge structure etc. to enable recovery when manuscript jam (paper jam) occurs in automatic document feeder 25. In this arrangement, manuscript stacker 24 does not have sufficient strength and cannot endure the forces repeatedly exerted through frequent opening and shutting operations, possibly resulting in breakage. In other words, if the attempt to improve the operationality of the manuscript removal operation adversely entails degradation of the operationality for the opening and shutting operation of platen cover 21, then the user will selectively grasp any portion that is easy to hold and do the opening and shutting operation, as described above. This involves the possibility of breakage in manuscript stacker 24 which may not be sufficiently strong.